1. Field of the Invention
The present invention relates to a liquid crystal display apparatus, an antistatic method for a liquid crystal display apparatus, and an electronic apparatus. In particularly, the present invention relates to a transverse-electric-field liquid crystal display apparatus, an antistatic method for a liquid crystal display apparatus, and an electronic apparatus including the liquid crystal display apparatus.
2. Description of the Related Art
A liquid crystal display apparatus mainly includes a liquid crystal panel formed by sealing in liquid crystal between two glass substrates, that is, a TFT (Thin Film Transistor) substrate and a counter substrate. Specifically, polarizing plates and phase different plates are provided above and below the liquid crystal panel, an electrode pad that receives input signals is connected with an IC and a film-like circuit substrate that are connected to a drive circuit side, and a backlight unit is provided on a lower surface thereof.
In a liquid crystal display apparatus, particularly, in a relatively-small liquid crystal display apparatus used in an electronic apparatus such as a cellular phone and a digital camera (hereinafter, referred to as “set”), a transparent protective cover for protecting the liquid crystal display apparatus that is fragile is provided on the set side. In order to particularly enhance merchantability due to compactification of components surrounding the liquid crystal display apparatus, thinning and reduction in weight of the liquid crystal display apparatus, reduction in size of a circumferential non-display area along with expansion of a display portion (so-called narrowing of frame) have been demanded in recent years.
On the other hand, in order to improve display characteristics such as a viewing angle, a chromatic change, contrast, and the like, a transverse electric field system such as an IPS (In-Plane Switching) mode and an FFS (Fringe Field Switching) mode has been widely applied to a liquid crystal panel. In the transverse electric field system, liquid crystal molecules turn parallel to substrates when applied a voltage. Therefore, in addition to a wide viewing angle, the transverse electric field system has a feature that a hue change depending on a viewing direction and a hue change in all gradation from white to black are caused less and natural images can be displayed even when seen from any direction from right to left or up and down.
However, as a problem of the transverse electric field system, there can be pointed out the fact that a common electrode is not arranged on the opposed substrate side but incorporated into the TFT substrate side and therefore charges are accumulated on the counter substrate side due to static electricity caused by a touch of a finger or the like. When charges are accumulated on the counter substrate side, liquid crystal molecules that should normally turn to a transverse direction in the transverse electric field system turn to a vertical direction due to an electric field generated by a vertical potential difference due to static electricity, which causes display unevenness.
To prevent this problem, it is necessary to take measures to provide an antistatic layer by, for example, forming a film made of ITO (Indium Tin Oxide) on a surface of the counter substrate side or applying a conductive coating to the polarizing plate. Further, to cause the charges to escape from the ITO film on the surface or the antistatic layer for polarizing plate, it is additionally necessary to obtain conduction to GND (ground). For the conduction, a GND wire may be extended to a metal frame in some cases by means of soldering, a conductive spacer, a conductive tape, and the like in a case where a conductive frame made of metal, a conductive resin, or a resin applied with the conductive coating is arranged so as to surround the antistatic layer for polarizing plate or the ITO film.
Specifically, a structure in which the polarizing plate having the antistatic layer comes into contact with a frame having conductivity and being made of metal or the like via a polarizing plate-frame contact conductive portion and is connected to GND (grounded) via the frame is adopted (see, for example, Japanese Patent Application Laid-open No. 05-188388; hereinafter, referred to as Patent Document 1). Further, a structure in which instead of the polarizing plate having the antistatic layer on a surface thereof, a transparent conductive film such as an ITO film is used on the counter substrate is adopted (see, for example, Japanese Patent Application Laid-open No. 2001-147441; hereinafter, referred to as Patent Document 2).
However, when there is an attempt to adopt a structure in which a transparent resin is applied between the protective cover on the set side and the liquid crystal display apparatus to integrate the protective cover and the liquid crystal display apparatus and a mechanical strength is thus ensured while suppressing interface reflection due to an air layer therebetween, the following problems are caused in related art of Patent Documents 1 and 2.
That is, due to interference of the frame and the conductive tape that are located above the surface of the liquid crystal panel, the integration of the protective cover using a transparent resin and thinning of the transparent resin layer are inhibited. In addition, when a thickness of the transparent resin layer becomes thick uselessly due to the interference of the frame and the conductive tape, display performance such as spectral characteristics and transmittance are liable to be affected. Therefore, the structures above may be difficult to be applied.
Moreover, in a structure in which static electricity accumulated on the surface of the liquid crystal panel is caused to escape to the frame side, it is necessary to take into consideration a GND connection between the frame and a casing on the set side or a printed circuit board. For example, that structure has a form similar to a method used, from the past, for preventing an erroneous operation of a drive IC due to static electricity, not for the transverse electric field system (see, for example, Japanese Patent Application Laid-open No. 2000-171815; hereinafter, referred to as Patent Document 3). In this case, screws, claws of a metal frame, a conductive tape, a metal film, and the like are used for the GND connection to the casing on the set side or the printed circuit board.